Powerplant: F - Engine Electrical Systems

Front 1

Why is stranded wire used rather than solid wire in most powerplant electrical systems?

Back 1

Solid wire is likely to break when it is subjected to vibration.

Front 2

What two things must be considered in selection of wire size when making an electrical installation in an aircraft?

Back 2

The current–carrying capability of the wire and the amount of voltage drop that is caused by current flowing through the wire.

Front 3

Why are the wires in certain electrical installations twisted together?

Back 3

By twisting the wires together, the magnetic fields caused by current flowing in the wires are minimized.

Front 4

What is used to protect a wire bundle from chafing where it passes through a hole in a bulkhead or frame?

Back 4

A grommet around the edges of the hole.

Front 5

How are electrical wires protected where they pass through an area of high temperature?

Back 5

Wires passing through these areas are insulated with high temperature insulation, and the wires are enclosed in some type of protective conduit.

Front 6

What is the minimum separation that is allowed between a wire bundle and a fluid line that carries combustible fluid or oxygen?

Back 6

A minimum of six inches.

Front 7

What is the significance of the color of the solderless connectors that are used on electrical wires?

Back 7

The color of the insulation indicates the size of wire the connector will fit. Red terminals fit 22– through 18–gage wire, blue terminals fit 16– and 14–gage wire, and yellow terminals fit 12– and 10–gage wire.

Front 8

What is the maximum number of wire terminals that may be stacked on a single stud in a terminal strip?

Back 8

Four

Front 9

What is the purpose of the shielding that is used to encase some electrical wires?

Back 9

Shielding intercepts radiated electromagnet energy and carries it to ground so it will not interfere with any nearby sensitive electronic equipment.

Front 10

Why must a switch be derated if it is used in a circuit controlling a DC electric motor?

Back 10

The initial current flowing into a DC electric motor is much higher than the current the motor uses after the armature begins to rotate. Because of this high inrush current, the controlling switches must be derated.

Front 11

What is used as the rectifier to produce direct current in a DC generator?

Back 11

Brushes and a commutator.

Front 12

How does a vibrator–type voltage regulator control the output voltage of a DC generator?

Back 12

The strength of the magnetic field produced in the voltage regulator relay is proportional to the generator output voltage. When the voltage rises above the regulated value, the relay pulls the contacts open and inserts a resistor in the generator field circuit. The contacts vibrate open and closed, putting the resistor in and out of the field circuit to control the amount of voltage the generator produces.

Front 13

What is meant by paralleling the generators of a twin–engine aircraft?

Back 13

Adjusting the voltage of the generators so they will share the electrical load equally.

Front 14

What is meant by flashing the field of a DC generator?

Back 14

Restoring the residual magnetism to the frame of a generator by passing battery current through the field coils in the same direction it flows when the generator is producing current.

Front 15

What kind of rectifier is used in a DC alternator of the type that is used on most of the modern light airplanes?

Back 15

A full–wave, three–phase rectifier made up of six silicon diodes.

Front 16

What is used to maintain a constant frequency of the alternating current that is produced by an AC alternator driven by an aircraft turbine engine?

Back 16

A hydraulic constant–speed drive unit between the engine and the alternator.

Front 17

What three things must be synchronized before a three–phase AC generator can be connected to a bus that is being served by another generator?

Back 17

The voltage, the frequency, and the phase rotation of the generators.

Front 18

What must be done to reverse the direction of rotation of the armature of a DC electric motor?

Back 18

The current flow must be reversed through the armature or the field windings, but not through both of them.

Front 19

Does a series–wound DC motor have a high or a low starting torque?

Back 19

A high starting torque.

Front 20

Which aircraft electrical circuit does not normally contain a fuse or circuit breaker?

Back 20

The starter motor circuit.

Front 21

When removing a battery from an aircraft, which connection should be removed first?

Back 21

The ground connection must be disconnected first and connected last.

Front 22

What is meant by the effective voltage of sine wave alternating current?

Back 22

The value of the alternating current that is needed to produce the same amount of heat as this value of direct current.

Front 23

What is a starter–generator that is used with many of the smaller gas turbine engines?

Back 23

A single–engine–mounted component that serves as a starter for starting the turbine engine. When the engine is running, the circuitry can be shifted so it acts as a compound–wound generator.

Front 24

When should aircraft wiring be installed in a conduit?

Back 24

When the wiring passes through an area in the aircraft where open wiring could likely be damaged, such as through a wheel well.

Front 25

When should the brushes in a starter motor be replaced?

Back 25

When they have worn to one half of their original length

Front 26

How is the direction of rotation of a DC electric motor reversed?

Back 26

Reverse the polarity of the armature or the field, but not both

Front 27

What is used as the rectifier to produce direct current in a DC alternator?

Back 27

Six solid–state diodes

Front 28

Is a starter motor series–wound or shunt–wound?

Back 28

Series wound for maximum stalled–rotor torque

Front 29

What are two ways wires can be attached to the pins in a cannon plug?

Back 29

By soldering the wires into pots on the pins and sockets.

By crimping tapered pins onto the wires and inserting the pins into tapered holes in the pins and sockets

Front 30

What must be done to a DC generator, after it has been overhauled, before it can produce electricity?

Back 30

The field must be flashed to restore residual magnetism to the field frame so it can begin to produce current

Front 31

Why is it not necessary to flash the field of a DC alternator after it has been overhauled?

Back 31

Alternator field is excited by battery current and residual voltage is not used to start the alternator producing current

Front 32

What is meant by a trip–free circuit breaker?

Back 32

A circuit breaker that opens a circuit any time an excessive amount of current flows, regardless of the position of the circuit breaker's operating handle

Front 33

Which way should the toggle of a switch that controls the propeller pitch move to place the propeller in low pitch (high RPM)?

Back 33

Forward

Front 34

Why are protective covers placed over some switches in an aircraft electrical circuit?

Back 34

To prevent the switch from being inadvertently actuated